Human skin is an organ that protects the body from the influences of the external environment. A portion of that protective function is provided by an immune system specific to the skin—the so-called skin immune system—that protects the body from potentially harmful environmental influences including pathogens and transformed skin cells. The skin immune system may provide a localized response known as contact hypersensitivity (CHS), a systemic response known as delayed type hypersensitivity (DTH), or both.
Exposing skin to ultraviolet radiation of the sun, particularly UV-B radiation, may damage certain types of cells involved in the skin immune system. Such damage may at least partially suppress function of the skin immune system and, therefore, may result in UV-induced immunosuppression.
Langerhans cells are dendritic-like elements of the skin immune system that may function to present antigens to Th1-lymphocytes. Langerhans cells may be particularly affected by exposure to UV radiation. Exposure to UV radiation can cause changes in Langerhans cells that may contribute to UV-induced immunosuppression. For example, exposure to UV radiation may impair the ability of Langerhans cells to present antigens.
Cytokines are known to be involved in the development of contact hypersensitivity (CHS) and the suppression of contact hypersensitivity by UV radiation. For example, interleukin (IL)-10 is a cytokine produced by keratinocytes after the keratinocytes are exposed to UV radiation. IL-10 impairs Langerhans cell function and suppresses CHS. Also, IL-12 promotes a Th1-lymphocyte immune response and is involved in the induction of CHS. IL-12 can reduce the immunosuppressive effects of UV radiation. Furthermore, administration of IL-12 prior to UV treatment may counteract UV-induced systemic suppression of delayed type hypersensitivity (DTH).
Ectoin and ectoin derivatives may be used for the prophylaxis or treatment of UV-induced immunosuppression. Such compounds may be incorporated into compositions for topical administration.